Variant alleles and other genetic traits cause or influence human diseases. The Online Mendelian Inheritance in Man (OMIM) compendium of human genes and genetic disorders, for example, lists thousands of alleles that have been linked to human diseases. Both well-known diseases such as diabetes and lesser-known diseases such as Von Willebrand disease and Creutzfeldt-Jakob disease can have genetic causes.
Many companies now offer genetic testing to screen for genetically based diseases. This genetic testing can be valuable diagnostic tool, especially for patients that experience symptoms that can be caused by many different diseases. For example, if a patient experiences symptoms that could be caused by multiple sclerosis or fibromyalgia, a genetic test may help a doctor diagnose the cause correctly. The doctor can then prescribe an appropriate treatment based on the diagnosis.
Genetic testing typically involves a multi-step process. First, a blood sample (or tissue) is sent to a laboratory. Laboratory technicians isolate the DNA in the sample. Lab technicians then typically apply polymerase chain reaction (PCR) techniques to amplify the isolated DNA. The amplified DNA is sequenced. The DNA sequence is then compared to allele sequences known to be associated with certain diseases.
In general, it takes at least two weeks for a patient to receive the results of a genetic test from a commercial laboratory or research center. The price for a genetic test typically ranges from about $100 to $2,000, depending on the nature and complexity of the test. Tests for genetic attributes linked to over 2,500 diseases are currently commercially available.